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Not everything that looks odd is contamination. Oyster mycelium sweats yellow droplets, lion’s mane blushes pink and shiitake blocks turn brown on purpose. Search what you’re seeing to find out whether it’s normal or a contaminant — and what to do next.
Contamination basics
- Green mold (Trichoderma) is the most common contaminant in home grows; it starts white and turns green as it sporulates.
- Bacteria show up as wet, slimy patches with a sour smell, usually from over-wet grain or substrate.
- Cobweb mold is grey and wispy and spreads fast; it’s often treatable if caught early.
Penn State Extension has a detailed overview of green mold in mushroom cultivation.
FAQ
Should I open a contaminated bag indoors?
No. Seal it in a trash bag and dispose of it outdoors; opening it releases spores that can contaminate future grows.
Can I cut out a contaminated spot?
With bacteria and most molds the contamination runs deeper than you can see. Cobweb caught early can sometimes be spot-treated; most others are best discarded.
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